US8907318B2 - Resistance change memory - Google Patents
Resistance change memory Download PDFInfo
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- US8907318B2 US8907318B2 US13/665,681 US201213665681A US8907318B2 US 8907318 B2 US8907318 B2 US 8907318B2 US 201213665681 A US201213665681 A US 201213665681A US 8907318 B2 US8907318 B2 US 8907318B2
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- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/003—Cell access
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0004—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising amorphous/crystalline phase transition cells
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0007—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising metal oxide memory material, e.g. perovskites
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/02—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using elements whose operation depends upon chemical change
- G11C13/025—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using elements whose operation depends upon chemical change using fullerenes, e.g. C60, or nanotubes, e.g. carbon or silicon nanotubes
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- H01L27/2409—
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- H01L27/2481—
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/20—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/20—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes
- H10B63/22—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes of the metal-insulator-metal type
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/80—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays
- H10B63/84—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays arranged in a direction perpendicular to the substrate, e.g. 3D cell arrays
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
- G11C2013/0073—Write using bi-directional cell biasing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/70—Resistive array aspects
- G11C2213/71—Three dimensional array
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/70—Resistive array aspects
- G11C2213/72—Array wherein the access device being a diode
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/70—Resistive array aspects
- G11C2213/76—Array using an access device for each cell which being not a transistor and not a diode
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- H01L45/04—
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- H01L45/06—
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- H01L45/1233—
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
- H10N70/231—Multistable switching devices, e.g. memristors based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/821—Device geometry
- H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
Definitions
- the present invention relates to a resistance change memory having a variable resistive element or a phase-change element as a memory element.
- resistance change memories such as ReRAM (Resistive RAM) with a variable resistive element as a memory element and PCRAM (Phase change RAM) with a phase-change element as a memory element are attracting attention as a next-generation nonvolatile semiconductor memory.
- ReRAM Resistive RAM
- PCRAM Phase change RAM
- resistance change memories include (1) a memory cell array of a cross-point type, (2) a large memory capacity realized by three-dimensional integration, and (3) DRAM-like high-speed operation.
- the NAND flash memory as a file memory and DRAM as a work memory can be replaced by the resistance change memory.
- the memory element and the rectifying element are connected in series between a word line and a bit line (for example, see Jpn. Pat. Appln. KOKAI Publication Nos. 2005-136425, 2001-236781, 2008-282499, 2007-311772, and 2008-311663).
- a large current during application of a forward bias, a small current during application of a reverse bias, and a large breakdown voltage are required for the characteristic of the rectifying element in order to correctly perform the set/reset operation and the read operation.
- a resistance change memory comprises a first conductive line extending in a first direction, a second conductive line extending in a second direction which is crossed to the first direction, a cell unit including a memory element and a rectifying element connected in series between the first and second conductive lines, and a control circuit which is connected to both of the first and second conductive lines, wherein the control circuit controls a voltage to change a resistance of the memory element between first and second values reversibly, wherein the rectifying element is a diode including an anode layer, a cathode layer and an insulating layer therebetween.
- FIG. 1 illustrates a resistance change memory according to an embodiment of the invention
- FIG. 2 illustrates a cross-point type memory cell array
- FIG. 3 illustrates a cell unit
- FIGS. 4 and 5 illustrate connection relationships between a memory element and a rectifying element
- FIGS. 6 to 8 illustrate layouts of first and second control circuits
- FIG. 9 illustrates an operation of the resistance change memory
- FIG. 10 illustrates a device structure of a p-i-n diode
- FIG. 11 illustrates a device structure of an SIS diode
- FIGS. 12 and 13 illustrate a band structure
- FIGS. 14 and 15 illustrate an operation during a forward bias
- FIG. 16 illustrates an operation during a reverse bias
- FIG. 17 illustrates a relationship between a bias and a current value
- FIG. 18 illustrates an embodiment
- FIGS. 19 to 21 illustrate modifications
- FIG. 22 illustrates a device structure of an MIS diode
- FIGS. 23 and 24 illustrate a band structure
- FIGS. 25 and 26 illustrate an operation during a forward bias
- FIG. 27 illustrates an operation during a reverse bias
- FIG. 28 illustrates a device structure of an MIS diode
- FIG. 29 illustrates an effective work function of metal
- FIG. 30 illustrates an embodiment
- FIG. 31 illustrates a modification
- FIG. 32 illustrates an embodiment
- FIG. 33 illustrates a modification
- FIG. 34 illustrates a device structure of an SMIS diode
- FIGS. 35 and 36 illustrate a band structure
- FIGS. 37 and 38 illustrate an operation during a forward bias
- FIG. 39 illustrates an operation during a reverse bias
- FIG. 40 illustrates a device structure of an SMIS diode
- FIG. 41 illustrates a relationship between a bias and a current value
- FIG. 42 illustrates an embodiment
- FIG. 43 illustrates a modification
- FIG. 44 illustrates an embodiment
- FIG. 45 illustrates a modification
- FIG. 46 illustrates a device structure of an MIM diode
- FIG. 47 illustrates a band structure
- FIG. 48 illustrates an operation during a forward bias
- FIG. 49 illustrates an operation during a reverse bias
- FIG. 50 illustrates a device structure of an MIM diode
- FIG. 51 illustrates a band structure
- FIG. 52 illustrates an operation during a forward bias
- FIG. 53 illustrates an operation during a reverse bias
- FIG. 54 illustrates an embodiment
- the present invention is applied to a resistance change memory in which a memory element is a variable resistive element or a phase-change element.
- the variable resistive element means an element that is made of a material whose resistance value is changed by a voltage, a current, a heat, or the like.
- the phase-change element means an element that is made of a material whose physical property such as a resistance and a capacitance is changed by a phase change.
- phase change (phase transition) embraces the following meanings.
- phase-changing examples include a transition from a metal, an insulator, semiconductor, a ferroelectric material, a paraelectric material, a collector, a piezoelectric material, a ferromagnetic material, a ferrimagnetic material, a helimagnetic material, a paramagnetic material, or an antiferromagnetic material to a ferroelectric-ferromagnetic material, and a reverse transition thereof.
- variable resistive element includes a phase-change element.
- the variable resistive element mainly refers to an element made of a metal oxide, a metal compound, an organic thin film, carbon, carbon nanotube, and the like.
- the invention is applied to resistance change memories such as ReRAM with the variable resistive element as the memory element and PCRAM with the phase-change element as the memory element.
- resistance change memories which is a cross-point type memory cell array such as the three-dimensional integration have a DRAM-like high-speed operation and a large memory capacity.
- the memory element and the rectifying element are connected in series between the word line and the bit line in order to pass a current only through the selected memory element.
- Examples of methods for changing a resistance value of the memory element include a method in which the resistance value of the memory element is reversibly changed between at least a first value and a second value by changing a polarity of a voltage applied to the memory element, and a method in which the resistance value of the memory element is reversibly changed between at least a first value and a second value by controlling the value and time of a voltage applied to the memory element without changing the polarity of the voltage.
- the former is called a bipolar operation, and the latter is called a unipolar operation.
- the forward bias characteristics and the reverse bias characteristics of the rectifying element approximate to a line-symmetry to a current axis of I-V characteristics. Therefore, A diode with a MIM structure or a SIS structure, or a transistor with a bipolar transistor structure is used as the rectifying element.
- the bipolar operation is adopted in memories, such as a magnetic random access memory, in which a bi-directional current is required in writing the data. It is possible to apply the bipolar operation to the resistance change memory of the invention.
- the resistance change memory of the invention will be described using the unipolar operation in which the resistance value of the memory element is reversibly changed between at least the first value and the second value by controlling the value and time of the voltage applied to the memory element without changing the polarity of the voltage.
- a large current during the application of the forward bias, a small current during the application of the reverse bias, and a large breakdown voltage are required as characteristics of a rectifying element in order to correctly perform the set/reset operation and the read operation, when the unipolar operation is applied to the resistance change memory (hereinafter referred to as cross-point type resistance change memory) comprising the cross-point type memory cell array.
- the rectifying element when the rectifying element is formed by a p-n junction diode or a p-i-n diode, it is necessary to increase the thickness of the rectifying element in order to satisfy the above requirements.
- the thickness of the rectifying element increases, the aspect ratio of the trench formed after the processing of the rectifying element becomes large, which is disadvantageous as three-dimensional integration of memory cell arrays.
- the p-n junction diode means a diode that has a p-n junction and comprises a p-type semiconductor layer (anode layer) and an n-type semiconductor layer (cathode layer).
- the p-i-n diode means a diode in which an intrinsic semiconductor layer is provided between the p-type semiconductor layer (anode layer) and the n-type semiconductor layer (cathode layer).
- the rectifying element comprises the anode layer, the cathode layer, and an insulating layer disposed therebetween in order that the rectifying element thickness decrease sufficiently while the rectifying element characteristic is satisfied for the resistance change memory.
- the rectifying element comprises the following diode:
- the SIS diode has a stacked structure of a p-type semiconductor layer (anode layer), insulating layer, and n-type semiconductor layer (cathode layer).
- the MIS diode has a stacked structure of a metallic layer (anode layer), insulating layer, and n-type semiconductor layer (cathode layer).
- the MIS diode has a stacked structure of a metallic layer (cathode layer), insulating layer, and p-type semiconductor layer (anode layer).
- the SMIS diode includes all the elements of the MIS diode, the SMIS diode is categorized as an MIS diode.
- the SMIS diode has a stacked structure of a p-type semiconductor layer (anode layer), metallic layer (anode layer), and insulating layer-n-type semiconductor layer (cathode layer).
- the SMIS diode has a stacked structure of an n-type semiconductor layer (cathode layer), metallic layer (cathode layer), insulating layer, and p-type semiconductor layer (anode layer.
- the MIM diode has a stacked structure of a metallic layer (anode layer), insulating layer, and metallic layer (cathode layer).
- FIG. 1 illustrates a main part of a resistance change memory according to an embodiment of the invention.
- Resistance change memory (for example, chip) 1 comprises cross-point type memory cell array 2 .
- Cross-point type memory cell array 2 has a stacked structure of memory cell arrays.
- First control circuit 3 is disposed at one end in a first direction of cross-point type memory cell array 2
- second control circuit 4 is disposed at one end in a second direction intersecting the first direction.
- first and second control circuits 3 and 4 select one of stacked memory cell arrays based on a memory cell array selection signal.
- first control circuit 3 selects a row of cross-point type memory cell array 2 based on a row address signal.
- second control circuit 4 selects a column of cross-point type memory cell array 2 based on a column address signal.
- First and second control circuits 3 and 4 control data write/erasing/read with respect to a memory element in cross-point type memory cell array 2 .
- First and second control circuits 3 and 4 can perform the data write/erasing/read with respect to one of the stacked memory cell arrays, and can simultaneously perform the data write/erasing/read with respect to at least two or all the stacked memory cell arrays.
- the write is referred to as set and the erasing is referred to as reset. It is necessary for a resistance value in the set state to differ from a resistance value in the reset state, and it does not matter whether the resistance value in the set state is higher or lower than the resistance value in the reset state.
- a multi-level resistance change memory in which multi-level data is stored in one memory element can be implemented when one of the resistance values is selectively written during the set operation.
- Controller (host) 5 supplies a control signal and data to resistance change memory 1 .
- the control signal is fed into command interface circuit 6
- the data is fed into data input/output buffer 7 .
- the controller 5 may be disposed in chip 1 , or in a host (computer) that is different from chip 1 .
- Command interface circuit 6 determines whether the data from host 5 is command data based on the control signal. When the data from host 5 is command data, command interface circuit 6 transfers the data to state machine 8 from data input/output buffer 7 .
- State machine 8 manages an operation of resistance change memory 1 based on the command data. For example, state machine 8 manages a set/reset operation and a read operation based on the command data from host 5 .
- Controller 5 can also determine an operation result in resistance change memory 1 by receiving status information managed by state machine 8 .
- controller 5 supplies an address signal to resistance change memory 1 .
- the address signal includes the memory cell array selection signal, the row address signal, and the column address signal.
- the address signal is fed into first and second control circuits 3 and 4 through address buffer 9 .
- pulse generator 10 In response to a command from state machine 8 , pulse generator 10 outputs a voltage pulse or a current pulse necessary for the set/reset operation and the read operation at a predetermined timing.
- FIG. 2 illustrates a cross-point type memory cell array
- Cross-point type memory cell array 2 is disposed on semiconductor substrate (for example, silicon substrate) 11 .
- a circuit element such as a MOS transistor or an insulating film may be sandwiched between cross-point type memory cell array 2 and semiconductor substrate 11 .
- cross-point type memory cell array 2 comprises four memory cell arrays, M 1 , M 2 , M 3 , and M 4 stacked in a third direction (direction perpendicular to a principal surface of semiconductor substrate 11 ) by way of example, and it is necessary that at least two memory cell arrays be stacked.
- Memory cell array M 1 comprises cell units CU 1 that are arrayed in the first and second directions.
- memory cell array M 2 comprises arrayed cell units CU 2
- memory cell array M 3 comprises arrayed cell units CU 3
- memory cell array M 4 comprises arrayed cell units CU 4 .
- Each of cell units CU 1 , CU 2 , CU 3 , and CU 4 comprises a memory element and a rectifying element, which are connected in series.
- Conductive lines L 1 ( j ⁇ 1), L 1 ( j ), and L 1 ( j+ 1), conductive lines L 2 ( i ⁇ 1), L 2 ( 1 ), and L 2 ( i+ 1), conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1), conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1), and conductive lines L 5 ( j ⁇ 1), L 5 ( j ), and L 5 ( j+ 1) are disposed on semiconductor substrate 11 .
- the odd-numbered conductive lines that is, conductive lines L 1 ( j ⁇ 1), L 1 ( j ), and L 1 ( j+ 1), conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1), and conductive lines L 5 ( j ⁇ 1), L 5 ( j ), and L 5 ( j+ 1) are extended toward the second direction from the side of semiconductor substrate 11 .
- the even-numbered conductive lines that is, conductive lines L 2 ( i ⁇ 1), L 2 ( 1 ), and L 2 ( i+ 1) and conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1) are extended toward the first direction from the side of semiconductor substrate 11 .
- the conductive lines act as a word line or a bit line.
- Lowermost first memory cell array M 1 is disposed between first conductive lines L 1 ( j ⁇ 1), L 1 ( j ), and L 1 ( j+ 1) and second conductive lines L 2 ( i ⁇ 1), L 2 ( i ), and L 2 ( i+ 1).
- one of conductive lines L 1 ( j ⁇ 1), L 1 ( j ), and L 1 ( j+ 1) and conductive lines L 2 ( i ⁇ 1), L 2 ( i ), and L 2 ( i+ 1) acts as the word line, and the other acts as the bit line.
- Memory cell array M 2 is disposed between second conductive lines L 2 ( i ⁇ 1), L 2 ( i ), and L 2 ( i+ 1) and third conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1).
- one of conductive lines L 2 ( i ⁇ 1), L 2 ( i ), and L 2 ( i+ 1) and conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) acts as the word line, and the other acts as the bit line.
- Memory cell array M 3 is disposed between third conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) and fourth conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1).
- one of conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) and conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1) acts as the word line, and the other acts as the bit line.
- Memory cell array M 4 is disposed between fourth conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1) and fifth conductive lines L 5 ( j ⁇ 1), L 5 ( 1 ), and L 5 ( j+ 1).
- one of the conductive lines L 4 ( i ⁇ 1), L 4 ( i ), and L 4 ( i+ 1) and conductive lines L 5 ( j ⁇ 1), L 5 ( j ), and L 5 ( j+ 1) acts as the word line, and the other acts as the bit line.
- FIG. 3 illustrates a cell unit in two memory cell arrays.
- FIG. 3 illustrates, for example, cell units CU 1 and CU 2 in memory cell arrays M 1 and M 2 of FIG. 2 .
- configurations of the cell units in memory cell arrays M 3 and M 4 of FIG. 2 are similar to those of the cell units of memory cell arrays M 1 and M 2 of FIG. 2 .
- Each of cell units CU 1 and CU 2 comprises the memory element and the rectifying element, which are connected in series.
- connection relationships between the memory element and the rectifying element be identical to one another in all the cell units of one memory cell array.
- FIGS. 4 and 5 illustrate connection relationships between the memory element and the rectifying element.
- a total of 4 ways exist in the connection relationship between the memory element and the rectifying element that is, 2 ways exist in a positional relationship between the memory element and the rectifying element and 2 ways exist in an orientation of the rectifying element. Accordingly, for the cell units of the two memory cell arrays, patterns of 16 ways (4 ways ⁇ 4 ways) exist in the connection relationship between the memory element and the rectifying element.
- the lower side of the drawings is the semiconductor substrate side.
- connection relationship (c) will mainly be described below by way of example.
- FIGS. 6 and 7 illustrate a first example of a layout of the first and second control circuits.
- Memory cell array Ms corresponding to one of the layers of memory cell arrays M 1 , M 2 , M 3 , and M 4 of FIG. 2 comprises cell units CUs arrayed as illustrated in FIG. 6 .
- One end of cell unit CUs is connected to conductive lines Ls(j ⁇ 1), Ls(j), and Ls(j+1), and the other end is connected to conductive lines Ls+1(i ⁇ 1), Ls+1(i), and Ls+1(i+1).
- memory cell array Ms+1 comprises arrayed cell units CUs+1.
- One end of cell unit CUs+1 is connected to conductive lines Ls+1(i ⁇ 1), Ls+1(i), and Ls+1(i+1), and the other end is connected to conductive lines Ls+2(j ⁇ 1), Ls+2(j), and Ls+2(j+1).
- First control circuit 3 is connected to one end in the first direction of each of conductive lines Ls+1(i ⁇ 1), Ls+1(i), and Ls+1(i+1) through switch element SW 1 .
- switch circuit SW 1 comprises an N-channel FET (Field Effect Transistor) that is controlled by control signals ⁇ +1(i ⁇ 1), ⁇ +1(i), and ⁇ +1(i+1).
- Second control circuit 4 is connected to one end in the second direction of each of conductive lines Ls(j ⁇ 1), Ls(j), and Ls(j+1) through switch element SW 2 .
- switch circuit SW 2 comprises the N-channel FET that is controlled by control signals ⁇ s(j ⁇ 1), ⁇ s(j), and ⁇ s(j+1).
- Second control circuit 4 is connected to one end in the second direction of each of the conductive lines Ls+2(j ⁇ 1), Ls+2(j), and Ls+2(j+1) through switch element SW 2 .
- switch circuit SW 2 comprises the N-channel FET that is controlled by control signals ⁇ s+2(j ⁇ 1), ⁇ s+2(j), and ⁇ s+2(j+1).
- FIG. 8 illustrates a second example of a layout of the first and second control circuits.
- the layout of the second example differs from the layout of the first example in that first control circuits 3 are disposed at both ends in the first direction of each of the memory cell arrays Ms, Ms+1, Ms+2, and Ms+3 while second control circuits 4 are disposed at both ends in the second direction of each of the memory cell arrays Ms, Ms+1, Ms+2, and Ms+3.
- First control circuits 3 are connected to both ends in the first direction of each of conductive lines Ls+1(i ⁇ 1), Ls+1(i), and Ls+1(i+1) through switch elements SW 1 .
- switch circuit SW 1 comprises the N-channel FET that is controlled by control signals ⁇ +1(i ⁇ 1), ⁇ +1(i), ⁇ +1(i+1), ⁇ s+3(i ⁇ 1), ⁇ s+3(i), and ⁇ s+3(i+1).
- Second control circuits 4 are connected to both ends in the second direction of each of conductive lines Ls(j ⁇ 1), Ls(j), and Ls(j+1) through switch elements SW 2 .
- switch circuit SW 2 comprises the N-channel FET that is controlled by control signals ⁇ s(j ⁇ 1), ⁇ s(j), ⁇ s(j+1), ⁇ s+2(j ⁇ 1), ⁇ s+2(j), and ⁇ s+2(j+1).
- FIG. 9 illustrates two memory cell arrays.
- Memory cell array M 1 of FIG. 9 corresponds to the memory cell array M 1 of FIG. 2
- memory cell array M 2 of FIG. 9 corresponds to memory cell array M 2 of FIG. 2 .
- connection relationship between the memory element and the rectifying element in cell units CU 1 and CU 2 corresponds to connection relationship (c) of FIG. 4 .
- a write (set) operation performed to selected cell unit CU 1 -sel in memory cell array M 1 will be described.
- An initial state of selected cell unit CU 1 -sel is an erasing (reset) state.
- the reset state is a high-resistance state (100 k ⁇ to 1 M ⁇ ) while the set state is a low-resistance state (1 K ⁇ to 10 K ⁇ ).
- Selected conductive line L 2 ( i ) is connected to high-potential-side power supply potential Vdd, and selected conductive line L 1 ( j ) is connected to low-potential-side power supply potential Vss.
- non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) other than selected conductive line L 1 ( j ) are connected to power supply potential Vdd.
- non-selected conductive line L 2 ( i+ 1) other than selected conductive line L 2 ( i ) is connected to power supply potential Vss.
- Third non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) from the semiconductor substrate side are connected to power supply potential Vdd.
- set current I-set is passed from a constant current source to selected cell unit CU 1 -sel, and the resistance value of the memory element in selected cell unit CU 1 -sel changes from the high-resistance state to the low-resistance state.
- a voltage of 1 to 2 V is applied to the memory element in selected cell unit CU 1 -sel, and the current density of set current I-set passed through the memory element (high-resistance state) is set to a range of 1 ⁇ 10 5 to 1 ⁇ 10 7 A/cm 2 .
- non-selected cell units CU 1 -unsel in memory cell array M 1 the reverse bias is applied to the rectifying element (diode) in the cell unit, which is connected between non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) and non-selected conductive line L 2 ( i+ 1).
- non-selected cell units CU 2 -unsel in memory cell array M 2 the reverse bias is applied to the rectifying element (diode) in the cell unit, which is connected between non-selected conductive line L 2 ( i+ 1) and non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1).
- Selected conductive line L 2 ( i ) is connected to high-potential-side power supply potential Vdd, and selected conductive line L 1 ( j ) is connected to low-potential-side power supply potential Vss.
- non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) other than selected conductive line L 1 ( j ) are connected to power supply potential Vdd.
- non-selected conductive line L 2 ( i+ 1) other than selected conductive line L 2 ( i ) is connected to power supply potential Vss.
- Third non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) from the semiconductor substrate side are connected to power supply potential Vdd.
- reset current I-reset is passed from the constant current source to selected cell unit CU 1 -sel, and the resistance value of the memory element in selected cell unit CU 1 -sel changes from the low-resistance state to the high-resistance state.
- the voltage of 1 to 3 V is applied to the memory element in selected cell unit CU 1 -sel, and the current density of reset current I-reset passed through the memory element (low-resistance state) is set to a range of 1 ⁇ 10 3 to 1 ⁇ 10 6 A/cm 2 .
- non-selected cell units CU 1 -unsel in memory cell array M 1 the reverse bias is applied to the rectifying element (diode) in the cell unit, which is connected between non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) and non-selected conductive line L 2 ( i+ 1).
- non-selected cell units CU 2 -unsel in memory cell array M 2 the reverse bias is applied to the rectifying element (diode) in the cell unit, which is connected between non-selected conductive line L 2 ( i+ 1) and non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1).
- Set current I-set and reset current I-reset differ from each other.
- the voltage applied to the memory element in selected cell unit CU 1 -sel in order to produce set current I-set and reset current I-reset depends on a material for the memory element.
- Selected conductive line L 2 ( i ) is connected to high-potential-side power supply potential Vdd, and selected conductive line L 1 ( j ) is connected to low-potential-side power supply potential Vss.
- non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) other than selected conductive line L 1 ( j ) are connected to power supply potential Vdd.
- non-selected conductive line L 2 ( i+ 1) other than selected conductive line L 2 ( i ) is connected to power supply potential Vss.
- Third non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1) from the semiconductor substrate side are connected to power supply potential Vdd.
- read current I-read is passed from the constant current source to the memory element (high-resistance state or low-resistance state) in selected cell unit CU 1 -sel.
- the data (resistance value) of the memory element can be read by detecting a potential change at a sense node in passing read current I-read through the memory element.
- read current I-read be sufficiently smaller than set current I-set and reset current I-reset such that the resistance value of the memory element does not change during the read operation.
- the reverse bias is applied to the rectifying element (diode) in the cell unit which is connected between non-selected conductive lines L 1 ( j ⁇ 1) and L 1 ( j+ 1) and non-selected conductive line L 2 ( i+ 1), in non-selected cell units CU 1 -unsel in memory cell array M 1 .
- non-selected cell units CU 2 -unsel in memory cell array M 2 the reverse bias is applied to the rectifying element (diode) in the cell unit which is connected between non-selected conductive line L 2 ( i+ 1) and non-selected conductive lines L 3 ( j ⁇ 1), L 3 ( j ), and L 3 ( j+ 1).
- the rectifying element (non-ohmic element) used in the resistance change memory of the embodiment will be described in detail.
- the connection relationship between the memory element and the rectifying element in the cell unit is shown in (c) of FIG. 4 .
- the p-i-n diode will briefly be described as a comparative example.
- FIG. 10 illustrates a structure of the p-i-n diode.
- Electrode layer 12 , n-type semiconductor layer 13 , intrinsic semiconductor layer 14 , p-type semiconductor layer 15 , and electrode layer 16 are stacked on conductive line L 2 ( i ) extended in the first direction.
- Intrinsic semiconductor layer 14 is a semiconductor layer in which an impurity is not doped or a semiconductor layer that contains a negligible trace of impurity with respect to intrinsic carrier density.
- P-i-n diode D-pin comprises n-type semiconductor layer 13 , intrinsic semiconductor layer 14 , and p-type semiconductor layer 15 .
- Memory element 17 which is the variable resistive element or the phase-change element, and electrode layer 18 are stacked on electrode layer 16 .
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction.
- the reverse current of the p-i-n diode should be suppressed sufficiently in case of the reverse bias is applied during the set/rest operation.
- the thickness in the third direction of p-i-n diode D-pin is set to a range of 100 nm to 200 nm.
- n-type semiconductor layer 13 is set to 15 nm
- intrinsic semiconductor layer 14 is set to 120 nm
- p-type semiconductor layer 15 is set to 15 nm
- the thickness of p-i-n diode D-pin is set to 150 nm.
- the resistance change memory which is a next-generation memory
- the resistance change memory is manufactured by a rule of minimum line width of 30 nm or less, although a width of the trench formed after the processing of the rectifying element becomes 30 nm or less, a height of the trench (included the thickness of the memory element and electrode layer) exceeds 100 nm.
- the aspect ratio of the trench increases, which is disadvantageous as regards three-dimensional integration of cross-point type memory cell arrays.
- the thickness of the rectifying element should be 100 nm or less in order to realize three-dimensional integration of the cross-point type memory cell array.
- the following rectifying element realizes three-dimensional integration of the cross-point type memory cell array.
- FIG. 11 illustrates a structure of an SIS diode.
- SIS diode D-sis has a stacked structure of n-type semiconductor layer 13 , insulating layer 21 , and p-type semiconductor layer 15 .
- SIS diode D-sis is disposed on electrode layer 12
- electrode layer 16 is disposed on SIS diode D-sis
- memory element 17 is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on electrode layer 16
- electrode layer 18 is disposed on memory element 17 .
- the positional relationship between the memory element and the rectifying element and the structures of the memory element and the rectifying element may be changed in various ways as long as the rectifying characteristic of the rectifying element is not lost.
- the memory element and the rectifying element may be formed upside down, the cathode and anode of the rectifying element may be reversed, the electrode layer may be omitted or added, a barrier layer that suppresses diffusion of the impurity may be added, or a combination thereof may be performed.
- a memory function of utilizing an insulating characteristic change caused by a trap or ion movement may be added to the insulating layer constituting the SIS diode.
- SIS diode D-sis One of the features of SIS diode D-sis is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of SIS diode D-sis is set to 100 nm or less.
- the thickness in the third direction of SIS diode D-sis is set to a range of 25 nm to 100 nm.
- n-type semiconductor layer 13 is set to 15 nm
- insulating layer 21 is set to 1 nm
- p-type semiconductor layer 15 is set to 15 nm, thereby setting the thickness of SIS diode D-sis to 31 nm.
- the thickness of insulating layer 21 is determined based on the condition that a charge tunneling phenomenon (including both direct tunneling and FN (Fowler-Noldheim) tunneling) is generated between n-type semiconductor layer 13 and p-type semiconductor layer 15 .
- a charge tunneling phenomenon including both direct tunneling and FN (Fowler-Noldheim) tunneling
- the thickness of insulating layer 21 is set to a range of 0.1 to 3 nm.
- the thickness of insulating layer 21 is set to a range of 0.1 to 3 nm.
- Insulating layer 21 may include an impurity atom or a semiconductor/metal dot (quantum dot), which forms a defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- Insulating layer 21 may be formed by a single layer or plural layers. In case of insulating layer 21 is formed by plural layers, preferably the layers have different barrier heights or different permittivities.
- insulating layer 21 is formed by insulating layers 21 A and 21 B having different barrier heights.
- the insulating layer 21 A is made of SiO 2 having a thickness of 0.5 nm while insulating layer 21 B is made of TiO 2 having a thickness of 1 nm.
- the barrier height of insulating layer 21 A is higher than that of insulating layer 21 B.
- the reverse current of the SIS diode can be sufficiently suppressed against the reverse bias.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias.
- FIGS. 12 to 13 illustrate a band structure of the SIS diode.
- the SIS diode In case of the insulating layer is disposed between the p-type semiconductor layer and the n-type semiconductor layer, the SIS diode has the structure of FIG. 12 before band modulation, and has the structure of FIG. 13 after the band modulation.
- the insulating layer is made of SiO 2 having a thickness of 1 nm.
- the reverse current of the SIS diode can be sufficiently suppressed against the reverse bias of 1 V.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias of 1 V.
- the reverse bias characteristic can further be improved. That is, in applying the reverse bias, the reverse current decreases while the breakdown voltage increases as the insulating layer is thickened.
- FIG. 17 illustrates a relationship between a bias direction and a current value.
- the insulating layer is made of SiO 2 having a thickness of 0.5 nm (X of FIG. 17 ), 2 nm (Y of FIG. 17 ), and 3 nm (Z of FIG. 17 ).
- the current passed through the SIS diode can be suppressed against the reverse bias of about 0.8 V (A point of FIG. 17 ).
- the current is not passed through the SIS diode against the reverse bias of about 2 V (B point of FIG. 17 ).
- the current passed through the SIS diode can be suppressed against the reverse bias of about 3 V (C point of FIG. 17 ). It is not necessary that the SIS diode be completely turned off in the reverse bias. It is only necessary to pass the current through the SIS diode such that a set or reset error, or a read error is not occurred in the non-selected memory cell.
- the insulating film may have a thickness of 0.5 nm or less even if the reverse bias of 0.8 V is applied to the SIS diode.
- the reverse bias applied to the diode of the resistance change memory ranges from 0.8 V to 3 V (except for forming operation)
- the thickness of the insulating layer constituting the SIS diode ranges from 0.1 to 3 nm as described above.
- the thickness of the insulating layer is determined in consideration of the forward bias characteristic.
- the forward bias characteristics and the reverse bias characteristics of the SIS diode can be approximate to a line-symmetry to a current axis of I-V characteristics.
- the SIS diode may include an intrinsic semiconductor layer with 10 nm or less.
- the insulating layer is made of SiO 2 in the example, the same holds true for an insulating layer made of SiN or Al 2 O 3 .
- FIG. 18 illustrates a structure of the SIS diode.
- Electrode layer 12 , n-type semiconductor layer 13 , insulating layer 21 , p-type semiconductor layer 15 , and electrode layer 16 are stacked on conductive line L 2 ( i ) extended in the first direction.
- SIS diode D-sis comprises n-type semiconductor layer 13 , insulating layer 21 , and p-type semiconductor layer 15 .
- Memory element 17 which is the variable resistive element or the phase-change element, and electrode layer 18 are stacked on electrode layer 16 .
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction.
- the reverse current of the SIS diode should be suppress sufficiently, in case of the reverse bias is applied during the set/reset operation.
- the thickness of SIS diode D-sis in the third direction is set to a range of 25 nm to 100 nm.
- n-type semiconductor layer 13 is set to 15 nm
- insulating layer 21 is set to 1 nm
- p-type semiconductor layer 15 is set to 15 nm, whereby the thickness of SIS diode D-sis becomes 31 nm.
- FIGS. 19 to 21 illustrate modifications of the SIS diode of FIG. 18 .
- the structure of the SIS diodes of the modifications differ from the structure of the SIS diode of FIG. 18 in that intrinsic semiconductor layer 22 is provided.
- intrinsic semiconductor layer 22 is disposed between n-type semiconductor layer 13 and insulating layer 21 .
- intrinsic semiconductor layer 22 is disposed between insulating layer 21 and p-type semiconductor layer 15 .
- intrinsic semiconductor layers 22 are disposed between n-type semiconductor layer 13 and insulating layer 21 and between insulating layer 21 and p-type semiconductor layer 15 .
- intrinsic semiconductor layer 22 can further improve the reverse bias characteristic of the SIS diode. That is, the reverse bias characteristic can be suppressed within the permissible aspect ratio by the thickened intrinsic semiconductor layer and the thickened insulating film.
- the forward current is hardly passed, although the current can be considerably suppressed during the reverse bias. Therefore, in case of intrinsic semiconductor layer 22 is added while insulating layer 21 is thinned, the forward current can be increased, while the current is suppressed during the reverse bias.
- the p-type semiconductor layer and the n-type semiconductor layer, which constitute the SIS diode, are selected from the group of Si, SiGe, SiC, Ge, C, a III-V semiconductor such as GaAs, a II-VI semiconductor such as ZnSe, an oxide semiconductor, a nitride semiconductor, a carbide semiconductor, and a sulfide semiconductor.
- the p-type semiconductor layer is one of p-type Si, TiO 2 , ZrO 2 , InZnO X , ITO, SnO 2 containing Sb, ZnO containing Al, AgSbO 3 , InGaZnO 4 , ZnO.SnO 2 , or a combination thereof.
- the n-type semiconductor layer is one of n-type Si, NiO X , ZnO, Rh 2 O 3 , ZnO containing N, La 2 CuO 4 , or a combination thereof.
- the insulating layer constituting the SIS diode is selected from the following materials.
- a and B are identical or different elements and one of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, or a combination thereof.
- a and B are identical or different elements and one of Ai, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, or a combination thereof.
- the insulating layer constituting the SIS diode is preferably selected from the group of SiO 2 , SiN, Si 3 N 4 , Al 2 O 3 , SiON, HfO 2 , HfSiON, Ta 2 O 5 , TiO 2 , and SrTiO 3 .
- the insulating layer includes an insulating layer that contains an impurity atom or a semiconductor/metal dot (quantum dot), which forms a defect level.
- the conductive line that acts as the word line/bit line is made of W, WN, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, WSi X , TaSi X , PdSi X , ErSi X , YSi X , PtSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MhSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, TaN, LaNiO, Al, PtIrO X , PtRhO X , Rh, TaAlN, SiTiO X , WSi X , TaSi X , PdSi X , PtSi X , IrSi X , ErSi X , YSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MnSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe
- the memory element is made of a binary or ternary metal oxide or an organic material (including single-layer film and nanotube).
- the carbon material includes a single-layer film, nanotube, and a two-dimensional structure such as graphene and fullerene.
- the metal oxide includes A) Oxide and B) Oxynitride.
- the thickness of the rectifying element can be decreased to 1 ⁇ 2 to 1 ⁇ 3 that of the p-n junction diode and the p-i-n diode while the rectifying element has the sufficient rectifying characteristic.
- the reverse current of the SIS diode to which the reverse bias is applied decreases 10 2 or more compared with the p-n junction diode or p-i-n diode, to which the identical reverse bias is applied.
- the rectifying characteristic can be controlled by changing a Fermi level of the semiconductor.
- the Fermi level of the n-type semiconductor layer on the electron-injection side is relatively raised, and the Fermi level of the p-type semiconductor layer on the electron-reception side is relatively lowered, which allows an enhancement of the rectifying characteristic.
- the SIS diode comprises plural insulating layers, and the insulating layers differ from each other in the barrier height or the permittivity. Therefore, an on/off-ratio of the SIS diode can be improved by the different barrier heights or permittivities of the insulating layers and the impurity concentrations of the p-type semiconductor layer and n-type semiconductor layer.
- the on/off-ratio can also be improved by incorporating a trap level (a dot or a defect of the impurity or Si) in the single or plural insulating films asymmetrically.
- the forward current can be significantly improved by greatly thinning the insulating film.
- the current characteristic can be improved by the use of an extremely-thin insulating film (with a thickness of less than 1 nm) made of SiOx, SiNx, TiOx, NiOx, WOx, and the like, which are formed by natural oxidation or marginal oxidation or nitridation by SPA.
- the on/off-ratio means a ratio (I-forward/I-reverse) of forward current I-forward and reverse current I-reverse in case of the forward bias is equal to the reverse bias in an absolute value.
- FIG. 22 illustrates a first example of a structure of the MIS diode.
- MIS diode D-mis has a stacked structure of a p-type semiconductor layer 15 , insulating layer 21 , and metallic layer 23 .
- Electrode layer 16 is disposed on MIS diode D-mis, memory element 17 which is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on electrode layer 16 , and electrode layer 18 is disposed on memory element 17 .
- ReRAM variable resistive element
- PCRAM phase-change element
- the positional relationship between the memory element and the rectifying element and the structures of the memory element and the rectifying element may be changed in various ways as long as the rectifying characteristic of the rectifying element is not lost.
- the memory element and the rectifying element may be formed upside down, the cathode and anode of the rectifying element may be reversed, the electrode layer may be omitted or added, a barrier layer that suppresses diffusion of the impurity may be added, and a combination thereof may be performed.
- the memory function of utilizing the insulating characteristic change caused by a trap or ion movement may be added to the insulating layer constituting the MIS diode.
- MIS diode D-mis One of the features of MIS diode D-mis is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of MIS diode D-mis is set to 100 nm or less.
- the thickness in the third direction of MIS diode D-mis is set to the range of 25 nm to 100 nm.
- p-type semiconductor layer 15 is set to 15 nm
- insulating layer 21 is set to 1 nm
- metallic layer 23 is set to 10 nm, whereby the thickness of MIS diode D-mis becomes as thin as 26 nm.
- Metallic layer 23 is made of a material having a relatively small effective work function because the MIS structure is formed between metallic layer 23 and p-type semiconductor layer 15 . Specifically, in case of the effective work function of metallic layer 23 becomes small, the Fermi level of metallic layer 23 is raised. The Fermi level of metallic layer 23 is set higher than that of p-type semiconductor layer 15 .
- the thickness of insulating layer 21 is determined based on the condition that the charge tunneling phenomenon (including both direct tunneling and FN tunneling) is generated between p-type semiconductor layer 15 and metallic layer 23 .
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- Insulating layer 21 may include an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- Insulating layer 21 may be formed by a single layer or plural layers. In case of insulating layer 21 is formed by plural layers, preferably the layers have different barrier heights or different permittivities.
- FIG. 28 illustrates a second example of the structure of the MIS diode.
- MIS diode D-mis has a stacked structure of metallic layer 24 , insulating layer 21 , and n-type semiconductor layer 13 .
- MIS diode D-mis is disposed on electrode layer 12
- memory element 17 which is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on MIS diode D-mis
- electrode layer 18 is disposed on memory element 17 .
- MIS diode D-mis One of the features of MIS diode D-mis is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of MIS diode D-mis is set to 100 nm or less.
- the thickness in the third direction of MIS diode D-mis is set to the range of 25 nm to 55 nm.
- metallic layer 24 is set to 10 nm
- insulating layer 21 is set to 1 nm
- n-type semiconductor layer 13 is set to 15 nm, whereby the thickness of MIS diode D-mis becomes 26 nm.
- Metallic layer 24 is made of a material having a relatively large effective work function because the MIS structure is formed between metallic layer 24 and n-type semiconductor layer 13 . Specifically, in case of the effective work function of metallic layer 24 becomes large, the Fermi level of metallic layer 24 is lowered. The Fermi level of metallic layer 24 is set lower than that of n-type semiconductor layer 13 . Alternatively, the p-type semiconductor layer may be used in case of the metallic layer is used as a hole supply source.
- the thickness of insulating layer 21 is determined based on the condition that the charge tunneling phenomenon (including both direct tunneling and FN tunneling) is generated between metallic layer 24 and n-type semiconductor layer 13 .
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- Insulating layer 21 may include an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- Insulating layer 21 may be formed by a single layer or plural layers. When insulating layer 21 is formed by plural layers, preferably the layers have different barrier heights or different permittivities.
- a mechanism of operation of the MIS diode will be described by taking the structure of FIG. 22 as an example.
- FIGS. 23 and 24 illustrate a band structure of the MIS diode.
- the MIS diode In case of the insulating layer is disposed between the p-type semiconductor layer and the metallic layer, the MIS diode has the structure of FIG. 23 before the band modulation, and has the structure of FIG. 24 after the band modulation.
- the Fermi level of the metallic layer is higher than that of p-type semiconductor layer 15 .
- the insulating layer is made of SiO 2 having a thickness of 1 nm.
- the reverse current of the MIS diode can be sufficiently suppressed against the reverse bias of 1 V.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias of 1 V.
- the reverse bias characteristic can be further improved. That is, in applying the reverse bias, the reverse current decreases while the breakdown voltage increases as the insulating layer is thickened.
- the thickness of the insulating layer constituting the MIS diode ranges from 0.1 to 3 nm.
- the thickness of the insulating layer is determined in consideration of the forward bias characteristic.
- FIG. 29 illustrates a table of effective work functions of metallic materials.
- the Fermi level is raised in case of the effective work function becomes small, and the Fermi level is lowered in case of the effective work function becomes large.
- the Fermi level of the metallic layer should be set higher than that of the p-type semiconductor layer.
- the Fermi level of the metallic layer should be lower than that of the n-type semiconductor layer.
- the metal satisfying the condition mentioned above is selected from the materials of FIG. 29 .
- FIG. 30 illustrates a first example of the structure of the MIS diode.
- FIG. 30 corresponds to the MIS diode of FIG. 22 .
- Electrode layer 23 Metallic layer (electrode layer) 23 , insulating layer 21 , p-type semiconductor layer 15 , and electrode layer 16 are stacked on conductive line L 2 ( i ) extended in the first direction.
- MIS diode D-mis comprises metallic layer 23 , insulating layer 21 , and p-type semiconductor layer 15 .
- Memory element 17 which is the variable resistive element or the phase-change element, and electrode layer 18 are stacked on electrode layer 16 .
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction. That is, electrode layer 12 of FIG. 10 is used as metallic layer 23 of the MIS diode. As a result, the height of memory cell MC can be further decreased.
- the reverse current of the MIS diode should be sufficiently suppressed to the reverse bias applied during the set/reset operation.
- the thickness in the third direction of MIS diode D-mis is set to the range of 25 nm to 100 nm.
- metallic layer 23 is set to 10 nm
- insulating layer 21 is set to 1 nm
- p-type semiconductor layer 15 is set to 15 nm, whereby the thickness of MIS diode D-mis becomes 26 nm.
- FIG. 31 illustrates a modification of the MIS diode of FIG. 30 .
- the structure of the MIS diode of the modification differs from the structure of the MIS diode of FIG. 30 in that intrinsic semiconductor layer 25 is provided. Specifically, in the modification of FIG. 30 , intrinsic semiconductor layer 25 is disposed between insulating layer 21 and p-type semiconductor layer 15 .
- intrinsic semiconductor layer 25 can further improve the reverse bias characteristic of the MIS diode. That is, the reverse bias characteristic can be suppressed within the permissible aspect ratio by the thickened intrinsic semiconductor layer and the thickened insulating film.
- the forward current is hardly passed although the current can be considerably suppressed during the reverse bias. Therefore, in case of intrinsic semiconductor layer 25 is added while insulating layer 21 is thinned, the forward current can be increased while the current is suppressed during the reverse bias.
- the P-type semiconductor layer is set to 5 nm
- the intrinsic semiconductor layer is set to about 60 nm
- the insulating layer is made of an extremely-thin (1 nm or less) SiN having a low barrier height. Therefore, even if the metal layer is set to 10 nm, because the sum of the layers becomes about 75 nm, the reverse current can be suppressed by the effect of the intrinsic semiconductor while the current is increased.
- FIG. 32 illustrates a second example of the structure of the MIS diode.
- FIG. 32 corresponds to the MIS diode of FIG. 28 .
- Electrode layer 12 , n-type semiconductor layer 13 , insulating layer 21 , and metallic layer (electrode layer) 24 are stacked on conductive line L 2 ( i ) extended in the first direction.
- MIS diode D-mis comprises n-type semiconductor layer 13 , insulating layer 21 , and metallic layer 24 . That is, electrode layer 16 of FIG. 10 is used as metallic layer 24 of the MIS diode. As a result, the height of memory cell MC can be further decreased.
- Memory element 17 which is the variable resistive element or the phase-change element, and electrode layer 18 are stacked on MIS diode D-mis.
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction.
- the reverse current of the MIS diode should be sufficiently suppressed to the reverse bias applied during the set/reset operation.
- the thickness in the third direction of MIS diode D-mis is set to the range of about 20 nm to about 100 nm.
- n-type semiconductor layer 13 is set to 15 nm
- insulating layer 21 is set to 1 nm
- metallic layer 24 is set to 10 nm, whereby the thickness of MIS diode D-mis becomes 26 nm.
- FIG. 33 illustrates a modification of the MIS diode of FIG. 32 .
- the structure of the MIS diode of the modification differs from the structure of the MIS diode of FIG. 32 in that intrinsic semiconductor layer 25 is provided. Specifically, in the modification of FIG. 33 , intrinsic semiconductor layer 25 is disposed between insulating layer 21 and n-type semiconductor layer 13 .
- intrinsic semiconductor layer 25 can further improve the reverse bias characteristic of the MIS diode. That is, the reverse bias characteristic can be suppressed within the permissible aspect ratio by the thickened intrinsic semiconductor layer and the thickened insulating film.
- the forward current is hardly passed although the current can be considerably suppressed during the reverse bias. Therefore, in case of intrinsic semiconductor layer 25 is added while insulating layer 21 is thinned, the forward current can be increased while the current is suppressed during the reverse bias.
- the P-type semiconductor layer is set to 5 nm
- intrinsic semiconductor layer is set to about 60 nm
- the insulating layer is made of an extremely-thin (1 nm or less) SiN having a low barrier height. Therefore, even if the metal layer is set to 10 nm, because the sum of the layers becomes about 75 nm, the reverse current can be suppressed by the effect of the intrinsic semiconductor while the current is increased.
- the p-type semiconductor layer and the n-type semiconductor layer, which constitute the MIS diode are selected from the group of Si, SiGe, SiC, Ge, C, GaAs, an oxide semiconductor, a nitride semiconductor, a carbide semiconductor, and a sulfide semiconductor.
- the p-type semiconductor layer is one of p-type Si, TiO 2 , ZrO 2 , InZnO X , ITO, SnO 2 containing Sb, ZnO containing Al, AgSbO 3 , InGaZnO 4 , and ZnO.SnO 2 .
- the n-type semiconductor layer is one of n-type Si, NiO X , ZnO, Rh 2 O 3 , ZnO containing N, and La 2 CuO 4 .
- the insulating layer constituting the MIS diode is selected from the following materials.
- a and B are identical or different elements and one of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, or a combination thereof.
- a and B are identical or different elements and one of Ai, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, or a combination thereof.
- the insulating layer constituting the MIS diode is preferably selected from the group of SiO 2 , SiN, Si 3 N 4 , Al 2 O 3 , SiON, HfO 2 , HfSiON, Ta 2 O 5 , TiO 2 , and SrTiO 3 .
- each of the oxygen element and the nitrogen element has a concentration of 1 ⁇ 10 18 atoms/cm 3 or more.
- the insulating layer includes an insulating layer that contains an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- the conductive line that acts as the word line/bit line is made of W, WN, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, WSi X , TaSi X , PdSi X , ErSi X , YSi X , PtSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MhSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, TaN, LaNiO, Al, PtIrO X , PtRhO X , Rh, TaAlN, SiTiO X , WSi X , TaSi X , PdSi X , PtSi X , IrSi X , ErSi X , YSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MnSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe
- the electrode layer includes the metallic layer constituting the MIS diode (the electrode layer may also be used as the metallic layer).
- the metallic layer constituting the MIS diode is made of one of the following materials or a combination thereof:
- the memory element is made of a binary or ternary metal oxide or an organic material.
- the thickness of the rectifying element can be decreased to 1 ⁇ 3 to 1 ⁇ 5 that of the p-n junction diode and the p-i-n diode while maintaining the rectifying characteristic.
- the reverse current of the MIS diode to which the reverse bias is applied decreases 10 3 or more compared with the p-n junction diode or the p-i-n diode, to which the identical reverse bias is applied.
- One of the anode layer and cathode layer of the MIS diode is made of a metal while the other is made of a semiconductor, so that the rectifying characteristic can be controlled by adjusting the effective work function (Fermi level) of the metal and the Fermi level of the semiconductor.
- the Fermi level of the metallic layer on the electron-injection side is relatively raised, and the Fermi level of the p-type semiconductor layer on the electron-reception side is relatively lowered, which allows the rectifying characteristic to be enhanced.
- the Fermi level of the metallic layer on the electron-injection side is relatively raised, and the Fermi level of the n-type semiconductor layer on the electron-reception side is relatively lowered, which allows the rectifying characteristic to be enhanced.
- the p-i-n diode in case of the minimum line width becomes 30 nm or less, unfortunately a variation in characteristic is generated by a variation in impurity concentration of the semiconductor layer. On the other hand, in the MIS diode, the variation in characteristic is reduced because one of the anode layer and the cathode layer is made of a metal.
- one (metallic layer side) of the anode layer and the cathode layer is only considered for the depletion of the semiconductor layer, which contributes to a thinned diode.
- the MIS diode comprises plural insulating layers, and the insulating layers differ from each other in the barrier height or the permittivity. Therefore, the on/off-ratio of the MIS diode can be improved by the different barrier heights or permittivities of the insulating layers and the impurity concentrations of the p-type semiconductor layer and n-type semiconductor layer.
- the on/off-ratio can also be improved by incorporating the trap level (a dot or a defect of an impurity or Si) in the single or plural insulating films asymmetrically.
- the forward current can be significantly improved by extremely thinning the insulating film.
- the current characteristic can be improved by the use of an extremely-thin insulating film made of SiO x , SiN x , TiO x , NiO x , WO x , and the like, which are formed by natural oxidation or SPA.
- FIG. 34 illustrates a first example of a structure of the SMIS diode.
- SMIS diode D-smis has a stacked structure of p-type semiconductor layer 15 , insulating layer 21 , metallic layer 23 , and n-type semiconductor layer 13 .
- SMIS diode D-smis is disposed on electrode layer 12
- electrode layer 16 is disposed on SMIS diode D-smis
- memory element 17 which is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on electrode layer 16
- electrode layer 18 is disposed on memory element 17 .
- the positional relationship between the memory element and the rectifying element and the structures of the memory element and the rectifying element may be changed in various ways as long as the rectifying characteristic of the rectifying element is not lost.
- the memory element and the rectifying element may be formed upside down, the cathode and anode of the rectifying element may be reversed, the electrode layer may be omitted or added, a barrier layer that suppresses diffusion of the impurity may be added, or a combination thereof may be performed.
- the memory function of utilizing the insulating characteristic change caused by a trap or ion movement may be added to the insulating layer constituting the SMIS diode.
- SMIS diode D-smis One of the features of SMIS diode D-smis is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of SMIS diode D-smis is set to 100 nm or less.
- the thickness in the third direction of SMIS diode D-smis is set to the range of 35 nm to 100 nm.
- p-type semiconductor layer 15 is set to 15 nm
- insulating layer 21 is set to 1 nm
- metallic layer 23 is set to 10 nm, whereby the thickness of SMIS diode D-smis becomes 41 nm.
- Metallic layer 23 is made of a material having a relatively small effective work function because the MIS structure is formed between metallic layer 23 and p-type semiconductor layer 15 . Specifically, when the effective work function of metallic layer 23 becomes small, the Fermi level of metallic layer 23 is raised. The Fermi level of metallic layer 23 is set higher than that of p-type semiconductor layer 15 .
- the thickness of insulating layer 21 is determined based on the condition that the charge tunneling phenomenon (including both direct tunneling and FN tunneling) is generated between p-type semiconductor layer 15 and metallic layer 23 .
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- Insulating layer 21 may include an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- Insulating layer 21 may be formed by a single layer or plural layers. In case of insulating layer 21 is formed by plural layers, preferably the layers have different barrier heights or different permittivities.
- FIG. 40 illustrates a second example of the structure of the SMIS diode.
- SMIS diode D-smis has a stacked structure of p-type semiconductor layer 15 , metallic layer 24 , insulating layer 21 , and n-type semiconductor layer 13 .
- SMIS diode D-smis is disposed on electrode layer 12
- electrode layer 16 is disposed on SMIS diode D-smis
- memory element 17 which is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on electrode layer 16
- electrode layer 18 is disposed on memory element 17 .
- SMIS diode D-smis One of the features of SMIS diode D-smis is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of SMIS diode D-smis is set to 100 nm or less.
- the thickness in the third direction of SMIS diode D-smis is set to the range of 35 nm to 80 nm.
- p-type semiconductor layer 15 is set to 15 nm
- metallic layer 24 is set to 10 nm
- insulating layer 21 is set to 1 nm
- n-type semiconductor layer 13 is set to 15 nm, whereby the thickness of SMIS diode D-smis becomes 41 nm.
- Metallic layer 24 is made of a material having a relatively large effective work function because the MIS structure is formed between metallic layer 24 and n-type semiconductor layer 13 . Specifically, in case of the effective work function of metallic layer 24 becomes large, the Fermi level of metallic layer 24 is lowered. The Fermi level of metallic layer 24 is set lower than that of n-type semiconductor layer 13 .
- the thickness of insulating layer 21 is determined based on the condition that the charge tunneling phenomenon (including both direct tunneling and FN tunneling) is generated between metallic layer 24 and n-type semiconductor layer 13 .
- the thickness of insulating layer 21 is set to the range of 0.5 to 3 nm.
- the thickness of insulating layer 21 is set to the range of 0.1 to 3 nm.
- Insulating layer 21 may include an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- Insulating layer 21 may be formed by a single layer or plural layers. When insulating layer 21 is formed by plural layers, preferably the layers have different barrier heights or different permittivities.
- FIGS. 35 and 36 illustrate a band structure of the SMIS diode.
- the SMIS diode In case of the insulating layer is disposed between the p-type semiconductor layer and the metallic layer to bring the n-type semiconductor layer into contact with the metallic layer, the SMIS diode has the structure of FIG. 35 before the band modulation, and has the structure of FIG. 36 after the band modulation.
- the Fermi level of the metallic layer is higher than that of p-type semiconductor layer 15 . It is assumed that the insulating layer is made of SiO 2 having a thickness of 1 nm.
- the reverse current of the SMIS diode can be sufficiently suppressed against the reverse bias of 1 V.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias of 1 V.
- the reverse bias characteristic can further be improved. That is, in applying the reverse bias, the reverse current decreases while the breakdown voltage increases as the insulating layer is thickened.
- the thickness of the insulating layer constituting the SMIS diode ranges from 0.1 to 3 nm.
- the thickness of the insulating layer is determined in consideration of the forward bias characteristic.
- the Fermi level of the metallic layer should be higher than that of the p-type semiconductor layer in the SMIS diode of FIG. 34 , and that the Fermi level of the metallic layer should be lower than that of the n-type semiconductor layer in the SMIS diode of FIG. 40 .
- a metal satisfying the condition is selected from the materials of FIG. 29 .
- FIG. 41 illustrates a relationship between a bias direction and a current value.
- the MIS/SMIS diode characteristic and the SIS diode characteristic are compared to each other.
- the forward current passed through the MIS/SMIS diode is larger than the forward current passed through the SIS diode for the bias of 1 V (point A of FIG. 41 ) or more.
- the reverse current passed through the MIS/SMIS diode is substantially equal to the reverse current passed through the SIS diode for the bias of 3 V (point B of FIG. 41 ) or more.
- the forward current characteristic can be improved without degrading the reverse bias characteristic by adjusting the bias applied to the MIS/SMIS diode.
- the forward bias characteristics and the reverse bias characteristics of the SIS diode can be approximate to a line-symmetry to a current axis of I-V characteristics.
- the SIS diode may include an intrinsic semiconductor layer with 10 nm or less.
- FIG. 42 illustrates a first example of the structure of the SMIS diode.
- FIG. 42 corresponds to the SMIS diode of FIG. 34 .
- Electrode layer 12 , n-type semiconductor layer 13 , metallic layer 23 , insulating layer 21 , p-type semiconductor layer 15 , and electrode layer 16 are stacked on conductive line L 2 ( i ) extended in the first direction.
- SMIS diode D-smis comprises n-type semiconductor layer 13 , metallic layer 23 , insulating layer 21 , and p-type semiconductor layer 15 .
- Memory element 17 which is the variable resistive element or the phase-change element, and electrode layer 18 are stacked on electrode layer 16 .
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction.
- the reverse current of the SMIS diode should be sufficiently suppressed the reverse bias applied during the set/reset operation.
- the thickness in the third direction of SMIS diode D-smis is set to the range of 35 nm to 80 nm.
- n-type semiconductor layer 13 is set to 15 nm
- metallic layer 23 is set to 10 nm
- insulating layer 21 is set to 1 nm
- p-type semiconductor layer 15 is set to 15 nm, whereby the thickness of SMIS diode D-smis becomes 41 nm.
- FIG. 43 illustrates a modification of the SMIS diode of FIG. 42 .
- the structure of the SMIS diode of the modification differs from the structure of the SMIS diode of FIG. 42 in that intrinsic semiconductor layer 25 is provided. Specifically, in the modification of FIG. 43 , intrinsic semiconductor layer 25 is disposed between insulating layer 21 and p-type semiconductor layer 15 .
- intrinsic semiconductor layer 25 can further improve the reverse bias characteristic of the SMIS diode.
- FIG. 44 illustrates a second example of the structure of the SMIS diode.
- FIG. 44 corresponds to the SMIS diode of FIG. 40 .
- Electrode layer 12 , n-type semiconductor layer 13 , insulating layer 21 , metallic layer 24 , p-type semiconductor layer 15 , and electrode layer 16 are stacked on conductive line L 2 ( i ) extended in the first direction.
- SMIS diode D-smis comprises n-type semiconductor layer 13 , insulating layer 21 , metallic layer 24 , and p-type semiconductor layer 15 .
- Memory element 17 which is the variable resistive element or the phase-change element and electrode layer 18 are stacked on electrode layer 16 .
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction.
- the reverse current of the SMIS diode should be sufficiently suppressed to the reverse bias applied during the set/reset operation.
- the thickness in the third direction of SMIS diode D-smis is set to the range of 35 nm to 80 nm.
- n-type semiconductor layer 13 is set to 15 nm
- insulating layer 21 is set to 1 nm
- metallic layer 24 is set to 10 nm
- p-type semiconductor layer 15 is set to 15 nm, whereby the thickness of SMIS diode D-smis becomes 41 nm.
- FIG. 45 illustrates a modification of the SMIS diode of FIG. 44 .
- the structure of the SMIS diode of the modification differs from the structure of the SMIS diode of FIG. 44 in that intrinsic semiconductor layer 25 is provided. Specifically, in the modification of FIG. 44 , intrinsic semiconductor layer 25 is disposed between insulating layer 21 and n-type semiconductor layer 13 .
- intrinsic semiconductor layer 25 can further improve the reverse bias characteristic of the SMIS diode. That is, the reverse bias characteristic can be suppressed within the permissible aspect ratio by the thickened intrinsic semiconductor layer and the thickened insulating film.
- a Schottky diode (including an ohmic junction) may be formed between the semiconductor and the metal to finely adjust the current characteristic.
- the P-type semiconductor layer is set to 5 nm
- intrinsic semiconductor layer is set to about 60 nm
- the insulating layer is made of the extremely-thin (1 nm or less) SiN having the low barrier height. Therefore, even if the metal layer is set to 10 nm, because the sum of the layers becomes about 75 nm, the reverse current can be suppressed by the effect of the intrinsic semiconductor while the current is gained.
- the p-type semiconductor layer and the n-type semiconductor layer, which constitute the SMIS diode are selected from the group of Si, SiGe, SiC, Ge, C, GaAs, an oxide semiconductor, a nitride semiconductor, a carbide semiconductor, and a sulfide semiconductor.
- the p-type semiconductor layer is one of p-type Si, TiO 2 , ZrO 2 , InZnO X , ITO, SnO 2 containing Sb, ZnO containing Al, AgSbO 3 , InGaZnO 4 , and ZnO.SnO 2 .
- the n-type semiconductor layer is one of n-type Si, NiO X , ZnO, Rh 2 O 3 , ZnO containing N, and La 2 CuO 4 .
- the insulating layer constituting the SMIS diode is selected from the following materials.
- a and B are identical or different elements and one of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, or a combination thereof.
- a and B are identical or different elements and one of Ai, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, or a combination thereof.
- the insulating layer constituting the SMIS diode is preferably selected from the group of SiO 2 , SiN, Si 3 N 4 , Al 2 O 3 , SiON, HfO 2 , HfSiON, Ta 2 O 5 , TiO 2 , SrTiO 3 , or a combination thereof.
- each of the oxygen element and the nitrogen element has a concentration of 1 ⁇ 10 18 atoms/cm 3 or more.
- the insulating layer includes an insulating layer that contains an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- the conductive line that acts as the word line/bit line is made of W, WN, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, WSi X , TaSi X , PdSi X , ErSi X , YSi X , PtSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MhSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, TaN, LaNiO, Al, PtIrO X , PtRhO X , Rh, TaAlN, SiTiO X , WSi X , TaSi X , PdSi X , PtSi X , IrSi X , ErSi X , YSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MnSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe
- the electrode layer includes a metallic layer constituting the SMIS diode (the electrode layer may also be used as the metallic layer).
- the metallic layer constituting the SMIS diode is made of one of the following materials or a combination thereof:
- the memory element is made of a binary or ternary metal oxide or an organic material.
- the thickness of the rectifying element can be decreased to 1 ⁇ 3 to 1 ⁇ 5 that of the p-n junction diode and the p-i-n diode while the rectifying characteristic is maintained.
- the reverse current of the SMIS diode to which the reverse bias is applied decreases 10 3 or more compared with the p-n junction diode or the p-i-n diode, to which the identical reverse bias is applied.
- One of the anode layer and cathode layer of the SMIS diode is made of a metal while the other is made of a semiconductor, so that the rectifying characteristic can be controlled by adjusting the effective work function (Fermi level) of the metal and the Fermi level of the semiconductor.
- the Fermi level of the metallic layer on the electron-injection side is relatively raised, and the Fermi level of the p-type semiconductor layer on the electron-reception side is relatively lowered, which allows the rectifying characteristic to be enhanced.
- the Fermi level of the metallic layer on the electron-injection side is relatively raised, and the Fermi level of the n-type semiconductor layer on the electron-reception side is relatively lowered, which allows the rectifying characteristic to be enhanced.
- the p-i-n diode in case of the minimum line width becomes 30 nm or less, unfortunately a variation in characteristic is generated by a variation in impurity concentration of the semiconductor layer. On the other hand, in the SMIS diode, the variation in characteristic is reduced because one of the anode layer and the cathode layer is made of a metal.
- the rectifying characteristic of the Schottky diode can be added to the rectifying characteristic of the MIS diode. Therefore, the rectifying characteristic of the SMIS diode can also be controlled by the impurity concentration of the semiconductor layer that is in contact with the metallic layer.
- the SMIS diode comprises plural insulating layers, and the insulating layers differ from each other in the barrier height or the permittivity. Therefore, the on/off-ratio of the SMIS diode can be improved by the different barrier heights or permittivities of the insulating layers and the impurity concentrations of the p-type semiconductor layer and n-type semiconductor layer.
- the on/off-ratio can also be improved by incorporating the trap level (a dot or a defect of an impurity or Si) in the single or plural insulating films asymmetrically.
- the forward current can be significantly improved by extremely thinning the insulating film.
- the current characteristic can be improved by the use of an extremely-thin insulating film made of SiO x , SiN x , TiO x , NiO x , WO x , and the like, which are formed by natural oxidation or SPA.
- FIG. 46 illustrates a structure of an MIM diode.
- MIM diode D-mim has a stacked structure of metallic layer 23 , insulating layers 21 A and 21 B, and metallic layer 24 .
- the positional relationship between the memory element and the rectifying element and the structures of the memory element and the rectifying element may be changed in various ways as long as the rectifying characteristic of the rectifying element is not lost.
- the memory element and the rectifying element may be formed upside down, the cathode and anode of the rectifying element may be reversed, the electrode layer may be omitted or added, a barrier layer that suppresses diffusion of the impurity may be added, or a combination thereof may be performed.
- the memory function of utilizing the insulating characteristic change caused by a trap or ion movement may be added to the insulating layer constituting the MIM diode.
- the barrier height (or electron affinity) of the material for insulating layer 21 A differs from the barrier height (or electron affinity) of the material for insulating layer 21 B.
- the barrier height of the material for insulating layer 21 A is higher than that of the material for insulating layer 21 B.
- metallic layers 23 and 24 have different effective work functions.
- the effective work function of metallic layer 23 is set larger than that of metallic layer 24 .
- the Fermi level of metallic layer 23 is lower than that of metallic layer 24 .
- Memory element 17 which is the variable resistive element (ReRAM) or the phase-change element (PCRAM) is disposed on MIM diode D-mim, and electrode layer 18 is disposed on memory element 17 .
- ReRAM variable resistive element
- PCRAM phase-change element
- MIM diode D-mim One of the features of MIM diode D-mim is that the reverse current caused by the reverse bias can be sufficiently suppressed during the set/reset operation even if the thickness in the third direction of MIM diode D-mim is set to 100 nm or less.
- the thickness in the third direction of MIM diode D-mim is set to the range of 10 nm to 30 nm.
- metallic layer 23 is set to 10 nm
- the sum of thickness of insulating layers 21 A and 21 B is set to 1 nm
- metallic layer 24 is set to 10 nm, whereby the thickness of MIM diode D-mim becomes 21 nm.
- the thickness of insulating layers 21 A and 21 B is determined based on the condition that the charge tunneling phenomenon (including both direct tunneling and FN tunneling) is generated between two metallic layers 23 and 24 .
- the sum of thickness of insulating layers 21 A and 21 B is set to the range of 0.5 to 3 nm.
- Insulating layers 21 A and 21 B may include an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- a fine rectifying element (non-ohmic element) that can be formed at a low temperature can be shrunk by the above structure.
- the number of insulating layers constituting the MIM diode is not limited to two, and the MIM diode may include at least three insulating layers. As illustrated in FIG. 50 , three insulating layers, 21 A, 21 B, and 21 C may be disposed between two metallic layers 23 and 24 .
- three insulating layers 21 A, 21 B, and 21 C have different barrier heights.
- An operation mechanism of the MIM diode will be described by taking the structure of FIG. 46 as an example.
- FIG. 47 illustrates a band structure of the MIM diode.
- insulating layer 21 A is made of SiO 2 having a thickness of 0.5 nm
- insulating layer 21 B is made of TiO 2 having a thickness of 1 nm.
- the reverse current of the MIM diode can be sufficiently suppressed against the reverse bias.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias.
- FIG. 50 An example of a structure of FIG. 50 will be described.
- FIG. 51 illustrates a band structure of the MIM diode.
- insulating layers 21 A, 21 B, and 21 C differ from one another in the barrier height.
- insulating layer 21 A is made of SiO 2 having a thickness of 0.5 nm
- insulating layer 21 B is made of TiO 2 having a thickness of 1 nm
- insulating layer 21 C is made of SiN having a thickness of 0.5 nm.
- the reverse current of the MIM diode can be sufficiently suppressed against the reverse bias.
- a sufficiently large forward current (set/reset current) can be obtained with respect to the forward bias.
- FIG. 54 illustrates a structure of the MIM diode.
- the structure corresponds to the MIM diode of FIG. 46 .
- Metallic layer (electrode layer) 23 , insulating layers 21 A and 21 B, and metallic layer (electrode layer) 24 are stacked on conductive line L 2 ( i ) extended in the first direction.
- MIM diode D-mim comprises metallic layer 23 , insulating layers 21 A and 21 B, and metallic layer 24 .
- Memory element 17 which is the variable resistive element or the phase-change element and electrode layer 18 are stacked on MIM diode D-mim.
- Conductive line L 3 ( j ) is disposed on electrode layer 18 , and extended in the second direction intersecting the first direction. That is, electrode layer 12 and electrode layer 16 of FIG. 10 are used as metallic layer 23 and metallic layer 24 of the MIM diode. As a result, the height of memory cell MC can be further decreased.
- the reverse current of the MIM diode should be sufficiently suppressed to the reverse bias applied during the set/reset operation.
- the thickness in the third direction of MIM diode D-mim is set to the range of 10 nm to 30 nm.
- metallic layer 23 is set to 10 nm
- the sum of thickness of insulating layer 21 A and 21 B is set to 1 nm
- metallic layer 24 is set to 10 nm, whereby the thickness of MIM diode D-mim becomes 21 nm.
- the insulating layers constituting the MIM diode are selected from the following materials.
- a and B are identical or different elements and one of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, or a combination thereof.
- a and B are identical or different elements and one of Ai, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, or a combination thereof.
- the insulating layer constituting the MIM diode is preferably selected from the group of SiO 2 , SiN, Si 3 N 4 , Al 2 O 3 , SiON, HfO 2 , HfSiON, Ta 2 O 5 , TiO 2 , SrTiO 3 , or a combination thereof.
- each of the oxygen element and the nitrogen element has a concentration of 1 ⁇ 10 18 atoms/cm 3 or more.
- the insulating layers have barrier heights that are different from one another.
- the insulating layer includes a material that contains an impurity atom or semiconductor/metal dot (quantum dot), which forms the defect level.
- the conductive line that acts as the word line/bit line is made of W, WN, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, WSi X , TaSi X , PdSi X , ErSi X , YSi X , PtSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MhSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, TiN, TaN, LaNiO, Al, PtIrO X , PtRhO X , Rh, TaAlN, SiTiO X , WSi X , TaSi X , PdSi X , PtSi X , IrSi X , ErSi X , YSi X , HfSi X , NiSi X , CoSi X , TiSi X , VSi X , CrSi X , MnSi X , FeSi X , or a combination thereof.
- the electrode layer is made of Pt, Au, Ag, TiAlN, SrRuO, Ru, RuN, Ir, Ti, V, Cr, Mn, Fe
- the electrode layer includes the metallic layer constituting the MIM diode (the electrode layer may also be used as the metallic layer).
- the two metallic layers constituting the MIM diode are made of one of the following materials:
- the two metallic layers have different effective work functions.
- one of the two metallic layers is made of a material selected from one of ErSi x , HfSi x , YSi x , TaC x , TaN x , TiN x , TiC x , TiB x , LaB x , La, LaN x , or a combination thereof which have a small effective work function
- the other is made of a material selected from one of WN x , W, WB x , WC x , Pt, PtSi x , Pd, PdSi x , Ir, and IrSi x , or a combination thereof which have a large effective work function.
- the memory element is made of a binary or ternary metal oxide.
- the thickness of the rectifying element can be decreased to 1 ⁇ 5 to 1/10 that of the p-n junction diode and the p-i-n diode while the rectifying characteristic is maintained.
- the reverse current of the MIS diode to which the reverse bias is applied decreases 10 3 or more compared with the p-n junction diode or p-i-n diode, to which an identical reverse bias is applied.
- Both the anode layer and cathode layer of the MIM diode are made of a metal, so that the rectifying characteristic can be controlled by adjusting the effective work function (Fermi level) of the metal.
- the p-i-n diode when the minimum line width becomes 30 nm or less, unfortunately a variation in characteristic is generated by the variation in impurity concentration of the semiconductor layer. On the other hand, in the MIM diode, the variation in characteristic is reduced because both the anode layer and the cathode layer are made of a metal.
- the depletion of the semiconductor layer is not considered, which contributes to a thinned diode.
- the MIM diode comprises plural insulating layers, and the insulating layers differ from each other in the barrier height or the permittivity. Therefore, the on/off-ratio of the MIS diode can be improved by the different barrier heights or permittivities of the insulating layers.
- the on/off-ratio can also be improved by incorporating the trap level (a dot or a defect of an impurity or Si) in the single or plural insulating films asymmetrically.
- the forward current can be significantly improved by extremely thinning the insulating film.
- the current characteristic can be improved by the use of an extremely-thin insulating film made of SiO x , SiN x , TiO x , NiO x , WO x , and the like, which are formed by natural oxidation or SPA.
- the resistance change memory of the embodiment has a high potential as a next-generation universal memory that replaces the current memories, such as the magnetic memory, the NAND flash memory, and the dynamic random access memory, which are used in commercially available products.
- the invention may be applied to a file memory in which the data can randomly be written at high speed, a mobile terminal that can download data at high speed, a portable player that can download data at high speed, a semiconductor memory for broadcasting equipment, a drive recorder, a home video, a large-capacity buffer memory for communication, and a semiconductor memory for a security camera.
- the rectifying element can be sufficiently thinned while satisfying the rectifying element characteristic required for the resistance change memory.
- the resistance change memory of the invention has a large advantage as a next-generation universal memory.
Abstract
Description
-
- SIS (Semiconductor-Insulator-Semiconductor) diode
-
- MIS (Metal-Insulator-Semiconductor) diode
-
- SMIS (Semiconductor-Metal-Insulator-Semiconductor) diode
-
- MIM (Metal-Insulator-Metal) diode
-
- SiO2, Al2O3, Y2O3, La2O3, Gd2O3, Ce2O3, CeO2, Ta2O5, HfO2, ZrO2, TiO2, HfSiO, HfAlO, ZrSiO, ZrAlO, AlSiO, or a combination thereof.
- AB2O4
-
- ABO3
-
- SiON, AlON, YON, LaON, GdON, CeON, TaON, HfON, ZrON, TiON, LaAlON, SrHfON, SrZrON, SrTiON, HfSiON, HfAlON, ZrSiON, ZrAlON, AlSiON, or a combination thereof.
- A material replaced some of the oxygen elements of the material in A) Oxide to a nitrogen element.
-
- SiO2, Al2O3, Y2O3, La2O3, Gd2O3, Ce2O3, CeO2, Ta2O5, HfO2, ZrO2, TiO2, HfSiO, HfAlO, ZrSiO, ZrAlO, AlSiO, or a combination thereof.
- AB2O4
-
- ABO3
-
- SiON, AlON, YON, LaON, GdON, CeON, TaON, HfON, ZrON, TiON, LaAlON, SrHfON, SrZrON, SrTiON, HfSiON, HfAlON, ZrSiON, ZrAlON, AlSiON, or a combination thereof.
- A material replaced some of the oxygen elements of the material in A) Oxide to a nitrogen element.
-
- SiO2, Al2O3, Y2O3, La2O3, Gd2O3, Ce2O3, CeO2, Ta2O5, HfO2, ZrO2, TiO2, HfSiO, HfAlO, ZrSiO, ZrAlO, AlSiO, or a combination thereof.
- AB2O4
-
- ABO3
-
- SiON, AlON, YON, LaON, GdON, CeON, TaON, HfON, ZrON, TiON, LaAlON, SrHfON, SrZrON, SrTiON, HfSiON, HfAlON, ZrSiON, ZrAlON, AlSiON, or a combination thereof.
- A material replaced some of the oxygen elements of the material in A) Oxide to a nitrogen element.
-
- SiO2, Al2O3, Y2O3, La2O3, Gd2O3, Ce2O3, CeO2, Ta2O5, HfO2, ZrO2, TiO2, HfSiO, HfAlO, ZrSiO, ZrAlO, AlSiO, or a combination thereof.
- AB2O4
-
- ABO3
-
- SiON, AlON, YON, LaON, GdON, CeON, TaON, HfON, ZrON, TiON, LaAlON, SrHfON, SrZrON, SrTiON, HfSiON, HfAlON, ZrSiON, ZrAlON, AlSiON, or a combination thereof.
- A material replaced some of the oxygen elements of the material in A) Oxide to a nitrogen element.
Claims (10)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US13/665,681 US8907318B2 (en) | 2009-06-12 | 2012-10-31 | Resistance change memory |
US14/560,968 US20150085562A1 (en) | 2009-06-12 | 2014-12-04 | Resistance change memory |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009141427A JP5388710B2 (en) | 2009-06-12 | 2009-06-12 | Resistance change memory |
JP2009-141427 | 2009-06-12 | ||
US12/755,891 US20100315857A1 (en) | 2009-06-12 | 2010-04-07 | Resistance change memory |
US13/665,681 US8907318B2 (en) | 2009-06-12 | 2012-10-31 | Resistance change memory |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/755,951 Continuation US20100261945A1 (en) | 2009-04-08 | 2010-04-07 | Method of separating aromatic compound from mixture containing aromatic compound and aliphatic compound |
US12/755,891 Continuation US20100315857A1 (en) | 2009-06-12 | 2010-04-07 | Resistance change memory |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/560,968 Continuation US20150085562A1 (en) | 2009-06-12 | 2014-12-04 | Resistance change memory |
Publications (2)
Publication Number | Publication Date |
---|---|
US20130070517A1 US20130070517A1 (en) | 2013-03-21 |
US8907318B2 true US8907318B2 (en) | 2014-12-09 |
Family
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Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/755,891 Abandoned US20100315857A1 (en) | 2009-06-12 | 2010-04-07 | Resistance change memory |
US13/665,681 Active US8907318B2 (en) | 2009-06-12 | 2012-10-31 | Resistance change memory |
US14/560,968 Abandoned US20150085562A1 (en) | 2009-06-12 | 2014-12-04 | Resistance change memory |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/755,891 Abandoned US20100315857A1 (en) | 2009-06-12 | 2010-04-07 | Resistance change memory |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/560,968 Abandoned US20150085562A1 (en) | 2009-06-12 | 2014-12-04 | Resistance change memory |
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US (3) | US20100315857A1 (en) |
JP (1) | JP5388710B2 (en) |
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Also Published As
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JP2010287789A (en) | 2010-12-24 |
US20130070517A1 (en) | 2013-03-21 |
US20100315857A1 (en) | 2010-12-16 |
JP5388710B2 (en) | 2014-01-15 |
US20150085562A1 (en) | 2015-03-26 |
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